Jet engine sound suppressor

ABSTRACT

An elongated tubular jet engine nozzle including inner wall surfaces, sound wave trap means extending along and spaced about said inner wall surfaces operative to effectively trap and absorb a majority of sound waves incident thereon along paths inclined 15* or more relative to the center line of the nozzle. The nozzle includes rigid sound wave reflecting surfaces spaced along and about the inner wall surfaces of the nozzle inclined at least 10* relative to the longitudinal center line of the nozzle and the reflecting surfaces are operative to reflect sound waves moving generally axially of the nozzle and incident thereon toward the remote inner wall surfaces and the associated sound wave trap means thereon along paths inclined more than 15* relative to the center line of the nozzle.

[ 51 May 30, 1972 [54] JET ENGINE SOUND SUPPRESSOR Claud R. Killian, R.F.D. No. 2, Hayesville, NC. 28904 [22] Filed: Apr. 13, 1971 [21] Appl.No.: 133,663

[72] Inventor:

Baruch.... ..18l/5O Ehrich ..181/48 3,508,838 4/1970 Martenson ..l8l/33 HB Primary Examiner-Robert S. Ward, Jr.

Att0rneyClarence A. OBrien and Harvey B. Jacobson [5 7] ABSTRACT An elongated tubular jet engine nozzle including inner wall surfaces, sound wave trap means extending along and spaced about said inner wall surfaces operative to effectively trap and absorb a majority of sound waves incident thereon along paths inclined 15 or more relative to the center line of the nozzle. The nozzle includes rigid sound wave reflecting surfaces spaced along and about the inner wall surfaces of the nozzle inclined at least 10 relative to the longitudinal center line of the nozzle and the reflecting surfaces are operative to reflect sound waves moving generally axially of the nozzle and incident thereon toward the remote inner wall surfaces and the associated sound wave trap means thereon along paths inclined more than 15 relative to the center line of the nozzle.

9 Claims, 4 Drawing Figures Patented May 30, 1972 2 Sheets-Sheet 1 (laud R. Kill/an by Mae/52% WWW 3M3"):

Patented May 30, 1972 I 3,666,044

2 Sheets-Sheet 2 /0 Cloud R. K ill/an WWW 3% J ET ENGINE SOUND SUPPRESSOR With the increasing use of jet engines to propel aircraft, greater aircraft flying hours being logged each year and the development of more powerful jet engines to propel faster and larger jet aircraft, attention has been centered on the noise emitted by jet engine aircraft, especially during take-ofi operations when the engines of substantially all aircraft are operated near or at their maximum power output.

Accordingly, a substantial need exists for a sound suppressing construction to be utilized in the formation of jet engine discharge nozzles whereby the noise emanating from jet engines may be appreciably reduced.

It is, therefore, the main object of this invention to provide a jet engine nozzle sound suppressing structure which will effectively reduce the sound emanating from a jet engine noule.

Another object of this invention is to provide a sound suppressing jet engine nozzle incorporating relatively simple structure and not requiring any special controls, although a controllable form of the invention with simple controls is also disclosed.

Another important object of this invention is to provide a sound suppressing jet engine tail pipe construction which may be readily incorporated into the construction of jet engines presently being manufactured and'added to jet engines already constructed.

A final object of this invention to be specifically enumerated herein is to provide a jet engine sound suppressing outlet nozzle or tail pipe which will conform to conventional forms of manufacture, be of simple construction and for the most part automatic in operation so as to provide a device that will be economically feasible, long lasting and relatively trouble free in operation.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

F IG. 1 is a perspective view of a jet engine having the sound suppressing outlet nozzle of the instant invention incorporated therein;

FIG. 2 is an enlarged fragmentary longitudinal vertical sectional view, taken substantially upon the plane indicated by the section line 22 of FIG. 1;

FIG. 3 is a transverse vertical sectional view, taken substantially upon the plane indicated by the section line 3-3 of FIG.

2; and

FIG. 4 is an enlarged fragmentary transverse vertical sectional view, taken substantially upon the plane indicated by the section line 44 of FIG. 2.

Referring now more specifically to the drawings, the numeral generally designates a jet engine including a rear exhaust nozzle 12. The exhaust nozzle 12 includes longitudinally and circumferentially extending inner wall surfaces 14.

Sound wave trap means referred to in general by the reference numeral 16 in the form of a plurality of longitudinally extending and slotted side by side tube members 18 are carried by the inner wall surfaces 14 of the outlet nozzle 12. The longitudinal slots formed in the tube members 18 are designated by the reference numerals 20 and the tubes or tubular members 18 are secured within the outlet nozzle 12 in any convenient manner.

From FIG. 4 of the drawings, it will be noted that the tubes or tubular members 18 are disposed in side by side contacting relation and that the slotted portions of the tubes 18 open generally radially inwardly toward the longitudinal center line of the outlet nozzle.

The sound wave trap means 16 further includes generally axially extending substantially right angle members 22 each consisting of a pair of generally right angled flanges 24. The angle members 22 are supported from the inner portions of the tubular members 18 in a manner such that the apexes on the right angle members 22 are disposed radially innermost and the free ends of the flanges 24 of the right angle members overlap the marginal portions of adjacent tubes 18 defining adjacent sides of the corresponding slots 20. The free edges of the flanges 24 include right angled anchoring flanges 26 and the free marginal edge portions of the flanges 24 of each right angle member 22 are interconnected by means of a web member 28 secured and extending therebetween, the adjacent marginal edges of adjacent tube member 18 being anchored between the opposite ends of the corresponding web member 28 and the associated anchor flanges 26. In this manner, the right angle members 22 are fixedly supported from the adjacent marginal edges of adjacent tubular members 18.

With attention now invited more specifically to FIGS. 2 and 3 of the drawings, a plurality of longitudinally and circumferentially spaced sound wave reflecting surface assemblies 30, 32 and 34 are supported from the tube members 18 and the right angle members 22.

The assemblies 30, 32 and 34 comprise inclined plates 36, 38 and 40, respectively, contoured to conform, in their inclined positions, to the internal configuration of the area bound by the right angle members 22. The plates 36, 38 and 40 are inclined with their inwardly facing surfaces also facing away from the discharge end 42 of the outlet nozzle 12. The marginal portions of the plates 36, 38 and 40 opposing the right angle members 22 may be secured to the latter in any convenient manner (not shown) and it may be seen that the plates 36, 38 and 40 are spaced apart toward the rear of the outlet noule and disposed at progressively smaller angles relative to the longitudinal center line of the nozzle 12. In addition, the plates 36 and 38 have notches 46 and 48 formed therein in which adjustable'flaps 50 and 52, respectively, are pivotally secured as at 54 and 56. The flaps 50 and 52 may be pivoted to positions substantially closing the notches 48 and with the flaps 50 and 52 contiguous with the plates 36, 38 and 40. A pair of fluid motors 58 and 60 are connected between the flaps 50 and 52 and adjacent right angle members 22 and may be suitably remotely controlled for swinging the flaps 50 and 52 from the positions thereof illustrated in FIG. 2 of the drawings to positions thereof with the flaps 50 and 52 more greatly inclined relative to the center line of the nozzle 12 than the corresponding plates 36 and 38,

It will be noted that the rear marginal edge portions of the plates 36, 38 and 40 terminate in outwardly inclined bracing flanges 66, 68 and 70 also contoured to conform, in their inclined positions, to the internal configuration of the nozzle 12 and having the marginal portions thereof supported, in any convenient manner, from the apexes of the right angle members 22. The notches 46 and 48 include portions thereof formed in the flanges 66 and 68 and the flaps 50 and 52 include flanges 72 and 74 which close those portions of the notches 46 and 48 defined in the flanges 66 and 68 when the flaps 50 and 52 are in the closed positions thereof illustrated in FIG. 2 of the drawings. Still further, the flaps 50 and 52 include side wall portions 50 and 52 slidingly received in the notches 46 and 48 during adjustment of the angulation of the flaps 50 and 52.

In operation, as the exhaust gases from the jet engine are discharged rearwardly to the rear end of the outlet nozzle 12, sound waves also pass rearwardly through the outlet nozzle 12. These sound waves move generally axially of the outlet nozzle and while portions of the sound waves immediately adjacent the inner wall surfaces 14 of the outlet nozzle 12 might be trapped and muffled by conventional structures, the instant invention utilizes the plates 36, 38 and 40 to reflect the sound waves passing rearwardly through the outlet nozzle 12 more sharply toward the remote inner wall surfaces 14 of the outlet nozzle 12. In this manner, as a sound wave strikes the plate 30 which is inclined approximately 30 relative to the longitudinal center line of the nozzle 12, the sound wave is reflected from the plate 30 at an angle of 30 relative thereto toward the remote inner side wall of the nozzle 12. However, the speed of the jet discharge from the nozzle 12 tends to in effect bend the reflected sound wave toward the outlet end of the nozzle 12 so that it strikes the plate 38 at an angle of perhaps 60 relative thereto to thus be reflected from the plate 38 at an angle of approximately 60 relative thereto whereby this reflected sound wave will be directed, even when deflected rearwardly by the speed of the jet exhaust through the nozzle 12, toward the opposing inner side wall 14 at an angle approaching 90 relative thereto. Of course, this reflected sound wave will then strike the right angle members 22 and be funnelled into the slots 20 leading into the interior of the tubular members 18. As the many times reflected sound wave enters the tubular members 18, it is trapped by the latter and absorbed within the tubular members 18. Of course, a series of plates 36, 38 and 40 may be spaced longitudinally of and about the outlet nozzle 12. Further, those axially moving sound waves which initially strike the plate 38 at an angle of approximately 30 relative thereto are reflected downwardly onto the plate 40 and thereafter back toward the opposing inner side wall portions 14 ofthe outlet nozzle for trapping and absorption by the tubular members 18 remote from the plate 40.

If it is desired, the fluid motors 58 and 60 may be actuated to further incline the flaps 50 and 52 relative to the center line of the outlet nozzle 12 whereby axially moving sound waves incident upon the flaps 50 and 52 will be even more sharply reflected toward the remote inner side wall surfaces 14 of the outlet nozzle 12. Of course, actuation of the fluid motors 58 and 60 may be readily accomplished by any suitable remotely located control point.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

What is claimed as new is as follows:

1. An elongated tubular jet engine nozzle including inner wall surfaces, sound wave trap means extending along and spaced about said inner wall surfaces operative to trap and absorb a majority of sound waves incident thereon along paths inclined to 15 or more relative to' the center line of the nozzle, and rigid sound wave reflecting surface means spaced along and about said inner wall surfaces inclined at least relative to the center line of said nozzle and facing upstream therein operative to reflect generally axially moving sound waves incident thereon toward the remote inner wall surfaces and associated sound wave trap means thereon along paths inclined more than relative to said center line.

2. The combination of claim 1 wherein said sound wave trap means includes generally axially extending longitudinally slotted tubular members supported from said inner wall surfaces in side by side relation and with the slots of said tubular members opening generally radially toward said center line of said nozzle.

3. The combination of claim 2 wherein said tubular members include converging edge portions defining said slots, elongated angle members extending along said nozzle between adjacent tubular members and positioned with their apexes innermost toward said center line and abridging the spacing between adjacent marginal edge portions of the slot of adjacent tubular members.

4. The combination of claim 1 wherein said sound wave reflecting surface means comprise inclined plates supported from said sound wave trap means and contoured to conform, in their inclined positions, to the internal configuration of said nozzle, said plates projecting inwardly from the corresponding sound wave trap means to points spaced radially of said center line.

5. The combination of claim 4 wherein the downstream marginal portions of said plates have transverse notches formed therein, and adjustable flaps pivotally secured in said notches for adjusted angular-displacement about axises extending transverse] of said nozzle, and motor means operatively connected etween said nozzle and said flaps for variably inclining the latter relative to said center line and the corresponding plates.

6. The method of reducing the sound emanating from the discharge nozzle of a jet engine, said method comprising the steps of lining the internal walls of the jet engine nozzle upstream from the discharge end thereof with sound wave trapping and absorbing structure and providing sound wave reflective surfaces within the discharge nozzle at points spaced therealong and thereabout with the sound wave reflecting surfaces being inclined relative to the center line of the nozzle and projecting generally radially inwardly from the sound wave absorbing lining to a point spaced radially outwardly from the center line of the discharge nozzle.

7. The combination of claim 1 wherein said sound wave trap means includes generally axially extending longitudinally slotted tubular members supported from said inner wall surfaces in side by side relation and with the slots of said tubular members opening generally radially toward said center line of said nozzle, said tubular members being generally cylindrical in cross-sectional shape.

8. The combination of claim 7 wherein said sound wave reflecting surface means comprise inclined plates supported from said sound wave trap means and contoured to conform, in their inclined positions, to the internal configuration of said nozzle, said plates projecting inwardly from the corresponding sound wave trap means to points spaced radially of said center line.

9. The combination of claim 8 wherein the downstream marginal portions of said plates have transverse notches formed therein, and adjustable flaps pivotally secured in said notches for adjusted angular displacement about axises extending transversely of said nozzle, and motor means operatively connected between said nozzle and said flaps for variably inclining the latter relative to said center line and the corresponding plates. 

1. An elongated tubular jet engine nozzle including inner wall surfaces, sound wave trap means extending along and spaced about said inner wall surfaces operative to trap anD absorb a majority of sound waves incident thereon along paths inclined to 15* or more relative to the center line of the nozzle, and rigid sound wave reflecting surface means spaced along and about said inner wall surfaces inclined at least 10* relative to the center line of said nozzle and facing upstream therein operative to reflect generally axially moving sound waves incident thereon toward the remote inner wall surfaces and associated sound wave trap means thereon along paths inclined more than 15* relative to said center line.
 2. The combination of claim 1 wherein said sound wave trap means includes generally axially extending longitudinally slotted tubular members supported from said inner wall surfaces in side by side relation and with the slots of said tubular members opening generally radially toward said center line of said nozzle.
 3. The combination of claim 2 wherein said tubular members include converging edge portions defining said slots, elongated angle members extending along said nozzle between adjacent tubular members and positioned with their apexes innermost toward said center line and abridging the spacing between adjacent marginal edge portions of the slot of adjacent tubular members.
 4. The combination of claim 1 wherein said sound wave reflecting surface means comprise inclined plates supported from said sound wave trap means and contoured to conform, in their inclined positions, to the internal configuration of said nozzle, said plates projecting inwardly from the corresponding sound wave trap means to points spaced radially of said center line.
 5. The combination of claim 4 wherein the downstream marginal portions of said plates have transverse notches formed therein, and adjustable flaps pivotally secured in said notches for adjusted angular displacement about axises extending transversely of said nozzle, and motor means operatively connected between said nozzle and said flaps for variably inclining the latter relative to said center line and the corresponding plates.
 6. The method of reducing the sound emanating from the discharge nozzle of a jet engine, said method comprising the steps of lining the internal walls of the jet engine nozzle upstream from the discharge end thereof with sound wave trapping and absorbing structure and providing sound wave reflective surfaces within the discharge nozzle at points spaced therealong and thereabout with the sound wave reflecting surfaces being inclined relative to the center line of the nozzle and projecting generally radially inwardly from the sound wave absorbing lining to a point spaced radially outwardly from the center line of the discharge nozzle.
 7. The combination of claim 1 wherein said sound wave trap means includes generally axially extending longitudinally slotted tubular members supported from said inner wall surfaces in side by side relation and with the slots of said tubular members opening generally radially toward said center line of said nozzle, said tubular members being generally cylindrical in cross-sectional shape.
 8. The combination of claim 7 wherein said sound wave reflecting surface means comprise inclined plates supported from said sound wave trap means and contoured to conform, in their inclined positions, to the internal configuration of said nozzle, said plates projecting inwardly from the corresponding sound wave trap means to points spaced radially of said center line.
 9. The combination of claim 8 wherein the downstream marginal portions of said plates have transverse notches formed therein, and adjustable flaps pivotally secured in said notches for adjusted angular displacement about axises extending transversely of said nozzle, and motor means operatively connected between said nozzle and said flaps for variably inclining the latter relative to said center line and the corresponding plates. 